Historically sewage treatment systems for multiple unit developments have conducted raw sewage through long conduits to a place far distant from the source. The sewage is then treated in open containers to encourage the proliferation of aerobic bacteria for the digestion of the sewage by converting organic material into simpler chemical compounds through the action of enzymes produced by the living organisms. Odoriferous gases, which are contained in the sewage and which are formed by decomposition, pervade the area of the sewage treatment facility. Moreover, the large, open tanks are unsightly. Consequently, it is to the greatest advantage to provide large sewage treatment facilities which are sufficiently far from populated areas to render the distasteful esthetics of the plant inobtrusive.
As population increases, such remote areas for sewage disposal plants become less and less available. Because of the distasteful nature of the plants, it has been the practice to create large branched collection networks which are served by large centralized disposal plants. Costs of effective sewage treatment are increased by the necessity of handling a large quantity of sewage in a small area and by the expense of the large collection networks of branch sewers, main sewers, trunk sewers and interceptors which serve centralized facilities. Discharge in outfall sewers from such facilities has been far heavier in pollutants than desired or than permissible.
Where limited amounts of funds are available for sewage treatment, the money required for construction of sewage collection and transportation systems subtracts from money available for sewage treatment. Thus, the systems of the prior art which require long range transportation of sewage to remote sewage plants have heretofore unresolved difficulties of high sewage transmission costs and inefficiency due to the need for processing large quantities of liquid at a single geographical location. New developments tend to overcrowd existing facilities and to reduce their effectiveness in treatment because of existing collection systems and existing interceptor sewers which provide ready communication to existing plants. New developments are often hampered and dictated by the availability to sewers connected to existing facilities or by the availability of land for building new treatment facilities. The most desirable developments from economic and geographic considerations are sometimes unavailing because of the lack of proper sewage collection systems.
Known small treatment plants which may be employed for industrial or housing developments employ open tanks. The esthetics of appearance and odors are major drawbacks which prevent installation of the facilities close to the waste water source. The unavailability of remote locations for installation of the small sewage systems and the expense and difficulty associated with obtaining remote locations for sewage treatment use have made such systems impractical.
Systems have been proposed for oxygenating sewage in sewer mains, trunks and interceptors to prevent sewage from becoming septic on its way to treatment facilities. Such systems augment rather than replace large centralized collection systems.
Heretofore, sewage treatment in small installations has been accomplished by small above ground plants or by smaller below ground plants which depend upon anaerobic digestion or which depend upon electric motors to physically stir sewage within a tank.
It is desirable that waste water be treated in many steps before effluent is released to the environment. Known small systems try to combine steps to maintain their small size. Usually the results are unsatisfactory. For example, septic tanks attempt to combine sedimentation for settling of sludge with the digestion of some of the sludge in a single tank. Outflow contains dissolved and suspended materials which are only partially decomposed. Decomposition continues in the effluent with the inherent noxious odors and clogging of dispersal facilities which are associated with septic tanks.
In small stirred aerobic tanks, the treatment is accomplished entirely by aerobic bacteria. Consequently, increased air is required, with attendant noise and power consumption requirement of auxiliary pumps and stirring motors. Often the effluent is not fully treated by the time of the release.
One problem with sewage treatment systems is the accumulation of non-digestable materials, such as personal hygiene objects, sand and grit, and other undigestable solid waste material. Such materials augment the sludge in the system and prevent or obstruct the contacting of the sludge with bacteria and the feeding of the bacteria with oxygen.
The problem has resulted in the rapid accumulation of sludge and undigested material and has required difficult sludge removing procedures.
The present invention is designed to provide a system which overcomes many of the problems of the prior art.